The invention relates generally to the field of slitters for slitting sheets of material. More particularly, the invention concerns a slitter cutting element uniformly biased about a blade carrier member by an elastomeric biasing member for precisely slitting thin sheets of media, such as photographic paper and film.
Conventional slitting devices used for slitting thin media, such as photographic paper and film, employ some sort of biasing member to control the contact force between cooperating blades or knife members. Typically such media is mass produced in large width master coils and then is cut to narrow width coils from the master coil using such slitting knives. Skilled artisans will appreciate that contact force is the force that one blade member exerts upon the other during a cutting operation.
Some success has been achieved in the art with a variety of biasing members, typically springs, presently used for biasing slitter blade members in an attempt to control the contact force between contacting blades. As shown in prior art FIGS. 1 and 2, the contact force between existing displaceable and stationary slitter knives or blade members 10, 12 is typically created by using a spring system 14 behind the displaceable blade member or knife 10. Various types of springs are currently in use, including coil 16 (illustrated in FIG. 3A), Belleville(trademark) 18 (illustrated in FIG. 4A), and garter 20 (illustrated in FIG. 5A). In each of these prior art devices, knives or blades 10, 12, are attached to a knife or blade carrier 22 via some sort of attachment, such as a retainer ring 24 (FIGS. 4A and 5A) or screws 26 (FIGS. 1-3A). Despite the progress accomplished with the above biasing members, a major shortcoming associated with each of these various biasing springs is that they create uneven spring forces around the circumference of the knife or blade member, as depicted in FIGS. 3B, 4B, and 5B. Experienced artisans will appreciate that these variations in spring force adversely affects the wear of the slitter knives as well as the quality of the slit edge.
Therefore, there persists a need in the art for a slitter element useable in an apparatus for slitting thin media, such as photographic paper and film, that provides uniform media slitting resulting from a uniform contact force between cooperating engaging blade members of the slitting device.
It is, therefore, an object of the invention to provide a slitter cutting element in which a blade member is uniformly biased about the circumference of a blade carrier.
It is another object of the invention to provide a slitter cutting element in which an elastomeric biasing member is arranged in biasing contact with the blade member.
It is yet another object of the invention to provide a slitter cutting element in which the elastomeric biasing member is bonded circumferentially to the blade carrier.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a slitter cutting element comprises:
a blade carrier; and,
a blade member arranged on the blade carrier, the blade member being biased by an elastomeric biasing member fixedly arranged in a recess formed in the blade carrier such that a portion of the elastomeric biasing member protrudes axially from the recess towards an inactive face of the blade member for continuous biasing contact with the inactive face of the blade member.
In another aspect of the invention, a method of making a slitter cutting element includes the steps of:
(a) providing a blade carrier; and,
(b) providing a blade member configured for arranging on the blade carrier;
(c) providing a elastomeric biasing member configured for arranging on the blade carrier;
(d) arranging the elastomeric biasing member on the blade carrier for continuous bias contact with a non-active face of the blade member; and,
(e) arranging the blade member on the blade carrier so that the non-active face is in intimate biasing contact with the elastomeric biasing member.
The present invention has numerous advantageous effects over prior art developments. First, when used in a slitter knife system, the circumferential force-deflection response of the elastomer spring is linear and more uniform compared with conventional spring designs.
Further, elastomeric slitter knife springs reduce the time required to set up a slitter knife assembly. Compared with conventional spring designs, no shimming, sorting, or other adjustments are required with elastomeric springs.
Also, elastomeric springs may be readily designed to have the desired force-deflection response. In general, elastomer springs appear to have more consistent force-deflection characteristics from spring to spring compared with coil and Belleville springs.
Moreover, a blade member biased by an elastomeric spring offers more uniform circumferential forces, longer life, elimination of fretting corrosion, and easier knife assembly.
Still further, conventional springs, such as the ones referred to above, are fabricated from metallic materials. During slitting, the motion of the springs relative to the metallic knife and collar causes fretting wear and corrosion. In manufacturing photographic products, the iron-based fretting wear debris generated by these spring materials is unacceptable. Slitter knife assemblies with elastomeric springs do not generate fretting wear debris.
Finally, since elastomers may be molded, the cross-sectional profile of the spring may be controlled to provide the desired force-deflection response. Because of their toughness, corrosion resistance, durability, resistance to compression set, wide range of durometer hardness, and ease of manufacture (e.g. casting or molding), polyurethane elastomers are particularly advantageous for spring applications.